Humans and gorillas last shared a common ancestor 10 million years ago, according to an analysis of the first full sequence of the gorilla genome. The gorilla is the last of the living great apes – humans, chimpanzees, gorillas and orangutans – to have its complete genetic sequence catalogued.

Scientists, led by researchers from the Wellcome Trust Sanger Institute near Cambridge and Baylor College of Medicine in Houston, also found that 15% of the gorilla's genome is closer between humans and gorillas than it is between humans and chimpanzees, our closest animal relative. The genomes of all three species are, in any case, highly similar: humans and chimpanzees share more than 98% of their genes, while humans and gorillas share more than 96%.

The genetic sequence was taken from a female western lowland gorilla (Gorilla gorilla gorilla) named Kamilah and published in Nature.

An initial analysis also showed similarities in genes involved in sensory perception and hearing, and brain development showed accelerated evolution in all three species. Genes associated with proteins that harden up skin were also particularly active in gorillas – which goes some way to explaining the large, tough knuckle pads on gorillas' hands.

"Gorillas are an interesting animal in their own right but the main reason they are of particular interest is because of their evolutionary closeness to us," said Aylwyn Scally, an author of the research from the Wellcome Trust Sanger Institute. "They're our second-closest evolutionary cousins after chimpanzees and knowing the content of the gorilla genome enables us to say quite a lot about an important period in human evolution when we were diverging from chimpanzees."

Comparing the sequences of humans, chimpanzees and gorillas has enabled scientists to put a more accurate clock on when the three species split from their last common ancestors. It was traditionally thought that the emergence of new species (known as "speciation") happens at a relatively localised point in time but emerging evidence suggests that this is not necessarily the case, that species split over an extended period. Studying the gorilla genome suggests that the divergence of gorillas from the common ancestor of humans and chimpanzees happened around 10 million years ago. Humans and chimpanzees last shared a common ancestor around 6 million years ago. Eastern and western gorillas split some time in the last million years.

One curious find was the evolution of genes associated with hearing, which seem very similar between humans and gorillas. "Scientists had suggested that the rapid evolution of human hearing genes was linked to the evolution of language," said Chris Tyler-Smith, senior author from the Wellcome Trust Sanger Institute. "Our results cast doubt on this, as hearing genes have evolved in gorillas at a similar rate to those in humans."

Scally adds that it could well be that there has been a parallel acceleration in these genes for two entirely different reasons – that human hearing has developed because of speech and gorilla hearing has developed to serve an entirely different, but as-yet-unknown, purpose.

The researchers said that studying the gorilla genome would shed light on a time when apes were fighting for survival across the world.

"There's an interesting background story of great ape evolution," says Scally. "The common ancestor of all four great apes was sometime back in 15 to 20 million years ago. At that time, it seems to have been a nice time to have been an ape – it was a golden age – a lot of the world was just right for the kind of environment for apes to live in. Since that time, the story has been of fragmentation and extinction – most of the great ape species that have existed have gone. Today, all the non-human apes are really endangered populations, they're living in forest refuges and population numbers are quite low. Humans look like an exception to that – we're all over the world now and live in places where you could never have had a primate beforehand."

Today, gorillas are classified as critically endangered and populations have plummeted to below 100,000 individuals in recent decades due to poaching and disease. They are restricted to equatorial forests in countries including Cameroon, Central African Republic, Gabon, Nigeria, Republic of Congo and Angola.

"As well as teaching us about human evolution, the study of great apes connects us to a time when our existence was more tenuous," say the researchers in Nature. "And in doing so, highlights the importance of protecting and conserving these remarkable species."

• This article was amended on 15 March 2012. The original used the term "genetic code" as a synonym for "genome". This has been corrected.